Chromium-51 is used in imaging red blood cells and has an effective half-life of 27 days. if a dose with an activity of 32 μci is given to a patient, how long will it take for the patient to have less than 8 μci present?

54 days

Explanation:

The half-life is the time need for the mass decrease by half. Thus, if the initial mass is m, after one half-live it will be m/2. Then, if another half-live pass, the m/2 mass will decrease by half, being m/4, and then successfully. After n half-lives, the final mass (M) is:

M = m/2ⁿ

So, if the final mass is 8μCi, and the initial is 32:

8 = 32/2ⁿ

2ⁿ = 32/8

2ⁿ = 4

n = 2

So, it's necessary to pass 2 half-lives, or 54 days to the mass decrease to 8μCi, thus after 54 days it will be less than 8μCi.

conduction is the transfer of thermal energy (heat in transfer) due to collisions between the molecules in the object. collisions between adjacent atoms and molecules transfer kinetic energy from the warmer to the cooler object. the objects must be in physical contact.